WASHINGTON - President Barack Obama on Monday challenged the US media stop chasing ratings and take on 2016 election candidates who are willing to "lie out loud" and whose campaigns are "untethered from reason."

Without calling out Donald Trump by name, Obama used a journalism award ceremony in Washington to deliver his toughest condemnation yet of the caustic tone of the presidential election campaign and the media coverage of it.

Training fire on television networks' often breathless coverage of Trump's campaign and wall-to-wall interviews with the controversial businessman, Obama said "a job well done is about more than just handing someone a microphone." He said the electorate would be better served if the media were to "probe and to question and to dig deeper and demand more."

"It would be better served if billions of dollars in free media (coverage) came with serious accountability," he added.

That was one in a string of clear references to the former reality TV star, who has leveraged his fame to appear almost constantly on television news. "What we are seeing right now does corrode our democracy and our society," Obama in remarks that were notable for their frankness and how much they reveal about the White House's unease.

"I'm not one who is faint of heart," Obama insisted. "But when our elected officials and our political campaigns become entirely untethered from reason and facts and analysis, when it doesn't matter what's true and what's not that makes it all but impossible for us to make good decisions on behalf of future generations."

The outgoing president dismissed disdain for political correctness - another common theme in Trump's campaign - as "increasingly just an excuse to say offensive things or lie out loud."

Obama pointed to the success of Oscar-wining journalism film "Spotlight" as evidence that the public still had a hunger for truth and respect for reporting. He also indicated that the tone of the debate, which has included harsh rhetoric against several foreign countries, was already having an impact.

Obama said that the first question he gets when he meets foreign leaders is often about what is going on in US politics.

Foreign leaders understand, he said, that "America is the place where you can't afford crazy politics."

The chaotic 2016 campaign has seen Trump brawl his way to victory over a host of more established Republican politicians in the race for the party nomination. He is now the firm favourite to face Democratic frontrunner Hillary Clinton in November's general election.